The objective of these studies is to assess the sensitivity of the human pituitary gland to hypothalamic gonadotropin releasing hormone (GnRH), and to quantitate circulating GnRH, in various physiologic and pathologic states. The following facets of the hypothalamic-pituitary system will be assessed: 1) the modulating effects of varying concentrations of gonadal steroids on the capacity of the pituitary to respond to GnRH; 2) possible changes in pituitary responsiveness to GnRH at various times postpartum; 3) differences in response to synthetic GnRH and other substances which affect hypothalamic function in normal subjects and patients with suspected benign or malignant hypothalamic-pituitary disease; 4) changes in radioimmunoassayable endogenous GnRH throughout the menstrual cycle, during the postmenopausal period, in patients with gonadal failure, and sequentially following gonadectomy during reproductive life; 5) sensitivity of the pituitary gland to GnRH in sleeping vs. awake states at various stages of life; and 6) the modulating effects upon pituitary responsiveness to GnRH in an in vitro system. In all studies, hormonal quantitation will be performed by radioimmunoassay.